Disparai — Camera Exposure and Sunny 16 | disparai.com
The three settings that decide an exposure, with the standard scales and the effect of doubling or halving each one.
Aperture is written as an f-number: f/1.0, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22. Each step is a factor of two in the light admitted, so f/11 passes twice the light of f/16 and f/8 passes four times as much. Aperture also sets depth of field: f/16 keeps a landscape sharp from foreground to horizon, f/2 isolates a face against a blurred background.
Shutter speed is written as a fraction of a second or as whole seconds: 1/1000, 1/500, 1/250, 1/125, 1/60, 1/30, 1/15, 1/8, 1/4, 1/2, 1 s. Each step doubles or halves the time the sensor or film is exposed, so 1/50 s passes twice the light of 1/100 s. Shutter speed also controls motion: 1/1000 s freezes a cyclist, 1/15 s renders them as a streak.
On narrow screens, swipe or scroll the plate sideways.
ISO is the sensitivity of the film or sensor, marked 50, 100, 200, 400, 800, 1600, 3200. Doubling the ISO records the same image in half the time, which is the same one-stop change as opening the aperture one step or doubling the shutter time. Each doubling also raises grain or noise by a measurable amount.
The three are coupled. If you open the aperture from f/16 to f/11 to let in more light, you must close it again, shorten the shutter, or lower the ISO to keep the same exposure. Because the exposure of a scene can be achieved with many combinations of aperture and shutter speed that admit the same amount of light, the triangle is a set of trade-offs rather than a single correct answer.
A useful way to read the triangle is as a budget: one stop of light can be spent on a wider aperture, a longer shutter, or a higher ISO, and each choice costs something else — shallower depth of field, more motion blur, or more grain.
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